fingercuff

A 1.5-2cm diameter cylinder of stiff woven material, such as plastic or reeds. A person's fingers fit snugly into each end. If the wearer tries to pull their fingers out, the cylinder lenghtens, and the diameter of the device gets smaller, holding the fingers tighter.

The best way to remove fingercuffs is to push the ends of the cylinder together, which will expand the diameter and allow the fingers to be easily removed (while the cuffs themselves are held open).

In the United States, the origin of the fingercuffs is associated with China, but in all likelihood the gadget is about as Chinese as the fortune cookie.